chore: postpone removal of window.ipfs v1 to 2019-09

We will revisit #589 in Q3,
for now we just move deprecation date to 2019-09-01

add-on/src/contentScripts/ipfs-proxy/page.js

@@ -35,7 +35,7 @@ function createWindowIpfs () {
   for (let cmd in proxyClient) {
     let fn = proxyClient[cmd]
     proxyClient[cmd] = function () {
-      console.warn('Calling commands directly on window.ipfs is deprecated and will be removed on 2019-04-01. Use API instance returned by window.ipfs.enable() instead. More: https://github.com/ipfs-shipyard/ipfs-companion/blob/master/docs/window.ipfs.md')
+      console.warn('Calling commands directly on window.ipfs is deprecated and will be removed on 2019-09-01. Use API instance returned by window.ipfs.enable() instead. More: https://github.com/ipfs-shipyard/ipfs-companion/blob/master/docs/window.ipfs.md')
       return fn.apply(this, arguments)
     }
   }